Skin on the arms that doesn’t wash off like dirt can be caused by friction, or it can be caused by chronic eczema, acanthosis nigricans, etc.
1. Friction: arm skin long-term friction, may produce hyperpigmentation, manifested as dirt like not wash off.
2. Chronic eczema: manifested in the affected area of the skin infiltration of dark red spots with pimples, scratches and scales, local skin thickening, surface roughness, and accompanied by varying degrees of erythroplasia, hyperpigmentation and so on. It will also be like dirt that can’t be washed away.
3. Acanthosis nigricans: the exact cause of this disease is not very clear, but may be related to endocrine disorders, sympathetic nerve disorders and other reasons. The skin color of the affected area is deepened to light gray, light brown or dark brown dry, rough and hypertrophic, and the surface may also have many tiny papillary elevations like velvet.
Arm skin like dirt can not be washed off may also be other skin diseases, burns and other causes of scarring or hyperpigmentation, if a long time does not fade or accompanied by itching, pain and other symptoms, it is recommended to go to the hospital in time for diagnosis and treatment.